[LMP] Accurate file resolving.
[LMP] Don't transcode the video stream.

The videostream could be an embedded album art, for example.
[LMP] Use taglib for tags copying on transcoding.

ffmpeg is quite kludgy with its concepts of streams, global metadata and
the likes.
[Util] Moved sysinfo.h to util/sys/
[Util] Use QSettings to parse /etc/os-release.